Arctotis fastuosa is a fast-growing annual that opportunistically responds to good rains at any time of the year. With plenty of water it will grow up to 600 mm high, but the size of the plant depends very much on the rain or water available. The soft herbaceous plants branch from the ground with long woolly leaves that are loosely grouped in small clumps. The deeply lobed leaves are up to 150 mm long and covered on both sides with white hairs, giving the plant a light, grey-green colour.

The large single flower heads are carried proudly at the top of long leafy stalks. The flower heads are very striking with a double row of brilliant, usually orange ray florets. The inner row of ray florets has dark blotches at their base which form a thick dark ring around the flat centre. The centre of the flower head is shining black when the inner disc florets are closed and yellow when they open. The outer ray florets can vary from plain orange, reddish orange, yellowish orange to cream-coloured. In nature, A. fastuosa germinates after good winter rains and colours large fields when it flowers in spring (July-October).

The small seeds (cypselae) look like tiny grape pips and ripen in the old flower heads about a month after flowering. A typical feature, visible under a microscope, of the fruit/seed of A. fastuosa is that it only has one cavity compared to the two of most other Arctotis species.